The present invention relates to a detector system for identifying among multiple magnetizable markers that may be embedded in other materials for sorting, authenticating, and/or sensing operations.
In the manufacture of a multi-component product, for example, packaged pharmaceuticals intended for over-the-counter sale, it is important to verify that the package includes a paper insert listing the characteristics of the drug and instructions for safe use. While considerable care is taken in placing the insert into the package, ideally, its presence in the package could be verified after the package is sealed. One way of doing this is by weighing the package to detect the additional weight of the insert. For light inserts or products that vary in weight, such an approach is unreliable.
The grandparent to the present application describes a method of verifying the presence of a component of a manufactured product by incorporating a small amount of filamentized magnetic material into that component, the latter whose presence may be detectable at a distance. The filaments are of low cost and may be freely dispersed into the material of the component for manufacturing convenience and may be remotely sensed even through packaging or the like. Unlike xe2x80x9cmagnetic stripexe2x80x9d type techniques for recording data, this invention allows identifying the component without direct contact.
While the ability to sense an individual component in a manufactured product is valuable, often it may be necessary to sense combinations of components or to distinguish between different component types. The parent to the present application describes a method of communicating not simply presence or absence of a component in an assembly, such an operation that requires only the conveyance of a single binary xe2x80x9cbitxe2x80x9d of information, but of distinguishing between different components containing different types of magnetizable filaments, each conveying one bit of multiple bits of information.
The number of different types of magnetic filaments that can be distinguished using previous techniques is limited. What is desired is an improved detection technique that allows a large number of different components to be distinguished from one another using magnetic marking techniques.
The present inventors have recognized that additional data may be extracted from the interrogation of magnetic filaments and other markers by capturing both amplitude and phase of the magnetic field induced in the markers. A phase-amplitude space may be divided into many distinct regions each of which may describe a unique combination of filament types and quantities, including mixtures of filament types. Further, an additional dimension of discrimination may be obtained by observing a phase-amplitude trajectory as the applied magnetic field is changed in effective strength, either directly, or as the indirect result of the materials carrying the magnetic markers moving into and out of the field region. In this way, a greater number of marked components may be successfully distinguished or single or multiple components authenticated.
Specifically, the present invention provides a detector system for magnetizable materials. The detector system includes an electromagnet coil adjacent to a volume sized to receive at least one type of magnetizable material. The coil produces a time-varying magnetic field having a first frequency component. A detection antenna adjacent to the volume detects time dependent variations in the magnetic field caused by the introduction of magnetizable material into the volume. Signal processing circuitry determines the amplitude and the phase of the magnetic field variation with respect to the first frequency component and amplitude of the magnetic field variation to provide an output signal dependent upon a predetermined classification of the amplitude and amplitude and phase into ranges.
It is thus one object of the invention to increase the amount of data that can be extracted from items marked by magnetizable materials. By capturing both amplitude and phase, better discrimination between material types may be had and a wider range of different marker types may be created using mixtures with different quantities of different magnetic material types.
The time varying magnetic field may also vary (as measured at the magnetic material) at a second frequency component lower than the first frequency component and the signal processing circuitry may determine amplitude and phase for a sequence of times during a period of the second frequency component to produce a phase-amplitude trajectory. In this case, the output signal may be a function of the path of the phase-amplitude trajectory entering and exiting the predefined ranges.
Thus it is another object of the invention to obtain yet additional information about the markers based on dynamic changes in amplitude and phase as the overall intensity of the magnetic field increases and decreases.
The predetermined range may be described by an inner and outer boundary and the output signal may require that the phase-amplitude trajectory pass into the inner boundary prior to setting the output signal and pass out of the outer boundary prior to resetting the output signal.
Thus, it is another object of the invention to provide hysteresis in the changing of the output signal so as to prevent signal fluctuation at the edges of a predefined range.
The magnetizable material may move with respect to the coil so as to create the variation of magnetic field at the second frequency component or the electrical power to the coil may be varied to create the second frequency component.
Thus it is another object of the invention to provide variation in the magnetic field needed to provide an added dimension of discrimination either through the movement of product on a conveyor belt or the like past the detection antenna and coil or by manipulation of the coil voltage directly for reading of stationary items.
Multiple predetermined ranges may be created to provide separate output signals where the ranges differ by amplitude range.
Thus, it is another object of the invention to be able to discriminate between different materials by the quantity of marker introduced into the detected component or the amplitude of the output signal.
Filaments of different magnetic materials may be incorporated in a single component of a product in different amounts so that a variety of different components provide different amplitude and phase.
Thus, it is another object of the invention to be able to encode information into an object by using a variety of magnetic filaments and different amounts and subsequently reading that encoded information.
Alternatively, the multiple output signals may be provided by predetermined ranges having a different phase angle.
Thus, it is another object of the invention to provide for distinguishing between components by use of different magnetic materials having different phase properties or by mixtures of different materials to create composite phase angles differing from the phase angles of either of the materials.
More generally, the output signal may require the passing of the phase-amplitude trajectory in predetermined order to at least two predefined ranges.
Thus, it is another object of the invention to provide for the detection of complex phase-amplitude trajectory behavior as may be incident to some materials or mixtures.
The signal processing circuitry may determine amplitude and phase with respect to the second frequency component.
Thus it is another object of the invention to provide yet another dimension of discrimination when the position of the magnetizable materials are known for the amplitude and phase to be used to determine the type and absolute amount of magnetizable material.
The output signal may indicate an amount of one species of magnetizable material or an amount of multiple species of magnetizable material, or relative proportions of multiple species of magnetizable material and magnetizable species of material.
Thus, it is another object of the invention to provide extremely flexible output signals for different applications of the inventive technique.
The detector may further include a display plotting amplitude and phase of the signal over the course of at least one cycle of the second frequency component and a drawing tool for drawing at least one region on the display over the plotted phase-amplitude trajectory so as to input a range of amplitude and phase of predefined range on the display. Alternatively, the region may be determined automatically based on the statistics of reference samples
Thus, it is another object of the invention to provide a means of teaching the detection system of the present invention to recognize particular combinations or types of magnetizable material on-site such as accommodates possible variations caused by local site environment or component environment.
The foregoing and other objects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention. Such embodiment does not necessary represent the full scope of the invention, however, and reference must be made to the claims herein for interpreting the scope of the invention.